Why must overhead glazing always be laminated?

A: Overhead (sloped) glazing must retain integrity after breakage so glass does not fall on people below. Laminated glass — with a PVB or SGP interlayer — holds broken fragments together (post-breakage retention), which is the decisive safety difference versus monolithic tempered glass that shatters into small granules.

For skylights and overhead glazing, the typical specification is laminated safety glass (e.g. 8+1.52PVB+8 or 10+1.90PVB+10), often combined with a metal catchment system as a tested backup. Heat-soaked tempered glass may be used in some overhead make-ups, but lamination is the default for safety-critical overhead zones.Related: Overhead & Skylight Safety Glass Guide

Does HST (heat soak test) guarantee zero nickel-sulfide breakage?

A: No. HST dramatically reduces the risk but cannot guarantee zero breakage.

Heat soak testing (typically 554°F / 290°C for around 4 hours) accelerates the detection of NiS inclusions, reducing the spontaneous breakage rate to below approximately 0.08%. It is a risk-control measure, not an elimination. For applications where post-breakage retention is essential (overhead, balustrades, overhead canopies), specify laminated glass in addition to or instead of relying on HST alone.Related: Tempered vs Laminated vs IGU

What is your tempered glass spontaneous breakage rate?

A: For heat-soaked tempered glass, the spontaneous breakage rate is below approximately 0.08%. For our laminated glass production line the stated rate is below 0.1%.

These are manufacturing-line figures, not a guarantee for an individual panel. Proper specification (HST for tempered, lamination for retention) and handling remain critical.Related: Certificates · Test Reports

Which international standards do your glass products comply with?

A: We manufacture and test to a range of internationally recognised standards. The applicable standard depends on the product and the project's target market:

• Tempered: EN 12150-2, ASTM C1048
• Laminated: EN 14449, ASTM C1172, ISO 12543
• IGU: EN 1279 (1–4), IGCC-referenced practice
• Structural / load: ASTM E1300
• Impact safety: EN 356 (e.g. P8A)

Certificates, test reports and warranty terms are available on the Certificates and Test Reports pages. Final acceptance is always subject to project specifications and local building codes.